CHEK1 and head and neck squamous cell carcinoma: In support of this, a study investigating the Chk1 inhibitor MK-8776 in non-small cell lung cancer and HNSCC cell lines prior to irradiation observed increased radiosensitisation of p53-mutant cell lines (H1299, CaLu-6, FaDu) but not of p53-wild-type tumour cells (A549 and H460), with DER values of 1.25–1.53 and 1.0–1.03, respectively [98].